Crashing to the floor. A 71.0 kg person falls straight down from a 1.60 m height
ID: 1692896 • Letter: C
Question
Crashing to the floor. A 71.0 kg person falls straight down from a 1.60 m height (measured from his feet) and lands with weight distributed equally on both feet. To soften the blow, he bends his knees so that it takes 0.180 s for him to stop once his feet touch the ground.a. What constant force does the floor exert on each foot while he's stopping?
b. Suppose instead that he lands stiff-legged and stops in only 0.100 s. What force does the floor now exert on each foot?
c. In which case is he more likely to sustain injury?
a. First
b. Second
Explanation / Answer
Crashing to the floor. A 71.0 kg person falls straight down from a 1.60 m height (measured from his feet) and lands with weight distributed equally on both feet. To soften the blow, he bends his knees so that it takes 0.180 s for him to stop once his feet touch the ground.a. What constant force does the floor exert on each foot while he's stopping? as the weight distributed equallly force on each leg=change in momentum/time =mass*velocity/time
the velocity acquired at the end of 1.60m= v0+2*9.8*1.6=2.366m/sec hence force that was exerted by the floor =[71/2 *2.366]/0.180=466.62N
b. Suppose instead that he lands stiff-legged and stops in only 0.100 s. What force does the floor now exert on each foot?
force that was exerted by the floor =[71/2 *2.366]/0.100=839.93N
force that was exerted by the floor =[71/2 *2.366]/0.100=839.93N
c. In which case is he more likely to sustain injury?
a. First
b. Second
second case he more likely to sustain injury